CVE-2002-1602 in screen
Summary
by MITRE
Buffer overflow in the Braille module for GNU screen 3.9.11, when HAVE_BRAILLE is defined, allows local users to execute arbitrary code.
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Analysis
by VulDB Data Team • 03/01/2025
The vulnerability identified as CVE-2002-1602 represents a critical buffer overflow flaw within the Braille module of GNU screen version 3.9.11. This issue specifically manifests when the HAVE_BRAILLE compilation flag is enabled, creating a pathway for local attackers to escalate privileges and execute malicious code on affected systems. The GNU screen utility serves as a terminal multiplexer that allows users to manage multiple terminal sessions within a single window, making it a fundamental component in many Unix-like operating systems and server environments where remote access and session management are essential.
The technical root cause of this vulnerability stems from improper input validation within the Braille module's handling of user-provided data. When the module processes Braille display configurations or related input parameters, insufficient bounds checking allows an attacker to overflow a fixed-size buffer allocated in memory. This buffer overflow occurs because the code does not adequately verify the length of incoming data before copying it into the allocated memory space. The flaw specifically affects the software's ability to handle Braille display configurations, which are typically used for accessibility purposes but in this case become a vector for code execution. The vulnerability falls under the CWE-121 category of stack-based buffer overflow, where the overflow occurs in stack memory and can be exploited to overwrite return addresses and function pointers.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with the ability to execute arbitrary code with the privileges of the GNU screen process. Since GNU screen is commonly used in server environments and often runs with elevated privileges, successful exploitation could lead to complete system compromise. Local attackers who already have access to the system can leverage this vulnerability to gain higher privileges, potentially allowing them to access sensitive data, modify system configurations, or establish persistent backdoors. The vulnerability is particularly concerning because it requires no special network access or authentication, making it an attractive target for attackers who have already gained local access through other means.
Mitigation strategies for CVE-2002-1602 should prioritize immediate patching of affected GNU screen installations to the latest stable versions that contain the necessary buffer overflow protections. System administrators should disable the Braille module entirely if it is not required for accessibility purposes by recompiling GNU screen without the HAVE_BRAILLE flag. Additionally, implementing proper input validation and bounds checking in the affected code sections would prevent similar vulnerabilities from occurring in future versions. The vulnerability demonstrates the importance of thorough code review processes, particularly for modules that handle external input data, and aligns with ATT&CK technique T1068 which covers privilege escalation through local exploitation. Organizations should also consider implementing runtime protections such as stack canaries and address space layout randomization to make exploitation more difficult even if patches are not immediately available. Regular security audits of system components and maintaining up-to-date software inventories are essential practices to prevent similar vulnerabilities from being exploited in production environments.